Hydraulic elevator safety device



April 25, 1961 c. BRANDON HYDRAULIC ELEVATOR SAFETY DEVICE Filed Au 19, 1959 United States Patent HYDRAULIC ELEVATOR SAFETY DEVICE Ca'rlBrandon, Detroit, Mich., assignmto Montgomery Elevator Company, a corporation of Delaware Filed Aug. 19, 1959-, Ser. No. 834,886 6 Claims. Cl. 121-46) This invention relates to a safety device for hydraulic elevators, and in particular it relates to a construction of the hydraulic cylinder and ram which prevents the base of the'ram from seating forcefully on the bottom of the cylinder. The present application is a continuation-inpart of my copending application 756,654, filed August 22, 1958.

Hydraulic elevators are normally extremely safe in operation, but it is possible for malfunction of the driving mechanism to cause the elevator to crash into the pit if escape of liquid from the hydraulic cylinder during descent is not stopped at the proper time by the control valves. When this occurs, the base of the elevator ram seats forcibly upon the bottom of the cylinder, and may cause damage to the bottom of the cylinder and base of the ram which is extremely expensive to repair. Likewise, such accidents are likely to cause injury to persons or freight in the elevator, and the possibility of serious damage is increased by reason of greater operating speeds of modern hydraulic elevators.

The present invention provides a very simple mechanism for rapidly decreasing the rate of escape of liquid from beneath the ram to the supply pipe for the cylinder if the ram overtravels its normal bottom limit and approaches dangerously close to the bottom of the cylinder.

In accordance with the present invention, a tapered safety ring is positioned in the lower end of the cylinder, with the minimum diameter of the tapered ring being very slightly greater than the diameter of the base of the ram. If the ram overtravels its normal bottom limit position, the base of the ram moving into the tapered ring causes a rapid decrease in the rate of escape of liquid from beneath the ram to the supply pipe.

Preferably the minimum diameter of the safety ring is a short distance above the bottom of the cylinder, and the lower portion of the ring cooperates with the bottom of the cylinder to provide a cushioning chamber from which liquid escapes only very slowly when the base of the ram reaches the top of the chamber. Obviously, the rate of escape of liquid from such a chamber depends on the clearance between the ram and the smallest part of the tapered ring. By maintaining a very small clearance between the base of the ram and the smallest part of the safety ring, it is possible to permit such very slow escape of liquid from below the ramthat, for all practical purposes, the ram is completely prevented from seating upon the bottom of the cylinder.

Preferably the bottom of the ram is provided with an outwardly extending flange forming a cushion ring which cooperates with a tapered safety ring in the upper end of the cylinder to prevent upward overtravel of the ram in accordance with my copending application 756,654.

The invention is illustrated in a preferred embodiment in the accompanying drawing, which is a fragmentary, vertical sectional view of the lower end of a hydraulic cylinder and ram in accordance with the present invention, part of the upper'end portion of the cylinder and ice ram also being shown to illustrate the liquid supply pipe for the cylinder. I

Referring to the drawing in greater detail, a hydraulic cylinder 5 has a bottom closure 6 which is welded in place as seen at 7, and a safety ring 8 is secured within the cylinder with its lower end 9 seated upon the closure 6. Safety ring 8 has its upper portion 10.tape red to a line of minimum diameter 11, and below the line 11 verted, and its tapered portion modification will be obvious to those a ring 8 has a portion of constant diameter 12.

Reciprocably mounted in cylinder 5 is a ram 13, said ram having a base 14 welded on its lower end, and an outwardly extending flange 15 on said base. It is apparent from the drawing that the maximum diameter of base 14 of the ram is only very slightly less than the minimum diameter 11 of safety ring 8. I

Near the upper end of cylinder 5 is .a liquid supply pipe 16 which isa part of conventional means for supplying liquid to the hydraulic cylinder. 'It'is apparent thaws l u dl um d m hec l e thmu h supply pipe '116'it willlift the motto raisethe elevator, while opening of bleed valves to permit escape of liquid from the cylinder through supply pipe 16 results in the ram moving downward to lower the elevator.

The control valves for downward travel of the elevator are intended to close automatically when the elevator reaches its lower limit of travel, i.e., the first floor level or basement level of the building in which the elevator is located. However, in the event of malfunction of the down travel control valves, it is apparent from the drawing that the present invention prevents damage to the ram, the cylinder, the elevator car or any persons or freight in the car. As base 14 of the ram enters the tapered portion 10 of safety ring 8, the rate of escape of liquid from beneath the ram to the supply pipe is rapidly decreased; and when the base of the ram reaches the line 11 of minimum diameter of the safety ring the lower portion 12 of the ring cooperates with the bottom closure 6 of the cylinder to form a cushioning chamber in the lower end of the cylinder from which liquid can escape only very slowly, thus preventing any possibility of the base of the ram seating forcefully upon the bottom of the cylinder.

As disclosed and claimed of which this is a division, ment can be used at the safety ring at the upper in the copending application a similar mechanical arrangeupper end of cylinder 5, the end of the cylinder being in- 10 cooperating with the outwardly extending flange 15 of ram base 14 to produce an increasing back pressure on the flange which ultimately becomes large enough to completely neutralize the lifting force on the ram in case the uptravel valves jam in open position and liquid continues to besupplied to the cylinder after the ram has reached the normal top limit of its travel.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom'for some skilled in the art.

I claim: -Q

1. In a hydraulic elevator system: a cylinder which has a tapered lower end portion and an imperforate lower end; a ram reciprocable in said cylinder, the diameter of said ram being substantially less than the diameter of the cylinder but only very slightly less than the minimum diameter of said tapered portion of the cylinder, and said ram having a generally planar, imperfor-ate base; and means including a supply pipe communicating with the upper portion of said cylinder to supply liquidunder pressure for reciprocating saidram, movement of the base of the ram into said tapered lowerend portion of the cylinder causing a rapid decrease in the rate ofescape of liquid-from beneath the ram to the supply pipe, whereby the ram is prevented from seatingforcefully on the bottom of the cylinder.

2. The device of claim 1 in which the tapered portion of the cylinder terminates a short distance above the bottom of the cylinder, the extreme lower end portion of the cylinder, below' said tapered portion, providing. a cushioning chamber from, which liquid escapes very slowly when the base of the ram reaches the top of said chamber.

' 3 The device of claim 2 in which the extreme lower end portion of the cylinder below the tapered portion is of uniform diameter only very slightly greater than the diameter of the ram. g

4. In a hydraulic elevator systemf a cylinder having an imperforate" lower end; a ram reciprocable insaid cylinder, said ram being of substantiallysmaller diameter than the cylinder and having a generally planar, imperforate base; means including a supply pipe communicating with the upper portion of said cylinder to supply liquid under pressure for reciprocating said ram; and an inwardly extending safety ring mounted in the lower end of the cylinder, said safety ring tapering from its upper margin toward its lower 'margin, and having a diameter very slightly greater-than the diameter of the 3 4 v base of the ram, movement of the base of the ram-into the safety ring causing a rapid decrease in the rate of escape of liquid from beneath the ram to the supply pipe, whereby the ram is prevented from seating forcefully on the bottom of the cylinder.

5. The device of claim 4 in which the taper of the safety ring terminates a short distance above the bottom of the cylinder, and the safety. ring has a lower portion which cooperates with the bottom of the cylinder to provide a cushioning chamber from which liquid escapes very slowly when the base of the ram reaches the top of said chamber. V

6. The device of claim 5 in which the safety ring has a lower end portion, below the tapered portion, which is of substantially uniform diameter.

References Cited in the file of this patent UNITED STATES PATENTS Bratz June -':l(),.'19 4 2, 

